A cast-iron cylindrical member is used for a cylinder liner for an internal combustion engine, a brake drum for an internal expanding drum brake, a bearing member, a supporting member, or the like. The cast-iron cylindrical member described above has an outer peripheral surface that is cast-in inserted with, for example, a metal material so that the cast-iron cylindrical member and a member (outer periphery-side member) provided on the outer peripheral surface side of the cast-iron cylindrical member are integrated. Therefore, for the purpose of improvement of bonding strength between the cast-iron cylindrical member and the outer periphery-side member and the like, a cast-iron cylindrical member having a plurality of projections formed on an outer peripheral surface thereof has been proposed (Patent Literature 1 to Patent Literature 3, and the like).
Shapes of the projections formed on the outer peripheral surface of the cast-iron cylindrical member and the like are varied. For example, a height of projections formed on an outer peripheral surface of a cast-in cylinder liner disclosed in Patent Literature 1 ranges from 0.5 mm to 1.0 mm. A height of projections formed on a cast-in member made of cast iron disclosed in Patent Literature 2 is set within a range of from 0.5 mm to 1.2 mm for use for cylinder liners.
Further, in Patent Literature 3, there is disclosed a cast-iron cylindrical member having an average value of the height of projections, which ranges from 0.25 mm to 0.85 mm, and the number of projections, which ranges from 55/cm2 to 152/cm2, as a test example. The technology described in Patent Literature 3 has an object to provide a cast-in structure having high thermal conductivity and high bonding strength, which can be reduced in thickness.